This invention refers to a laser resonator with first and second end mirrors and with coaxial electrodes between which laser radiation is reflected back and forth in the direction of an axis of symmetry of the laser resonator and passes azimuthally segment by segment through a resonator volume having an annular cross section.
Resonators of this type with a coaxial discharge structure are conventionally used for high-performance lasers, i.e. for lasers with up to several kW of laser power, and in particular for gas lasers such as CO.sub.2 lasers.
A laser resonator with an annular cross section on which the preamble of claim 1 is based is described in German Patent No. 41 23 024 C2. This laser resonator has coaxial, regular-cylindrical electrodes, with mirrors facing one another provided at their ends, between which the laser radiation travels azimuthally around the axis of symmetry of the resonator in the manner described above.
In this case, one of the end mirrors in particular can be directly connected to the inner electrode or be an integral part thereof, such that merely the outer electrode and the other end mirror have to be adjusted.
Aside from this, other resonators with an annular cross section are known, in which two or more mirrors are adjustable relative to the electrodes and to one another, German Patent No. 41 29 530 C2 or U.S. Pat. No. 5,353,299 are cited here as examples.
The radiation also travels azimuthally in the lasers known in these publications. The differences between the lasers and/or laser resonators known from the aforementioned publications lie primarily in the design of the end mirrors and in the manner in which the laser beam exits.
Another type of coaxial laser, which produces a laser beam with a cross section in the shape of a ring sector, is known from German Patent No. 44 21 600 A1. In this known laser additional mirrors for shaping the laser beam are required in addition to the two end mirrors. The amount of effort necessary to adjust the laser is correspondingly large.
A coaxial laser with a stable resonator, in which the laser radiation is guided over a very complex configuration of mirrors, such that an at least approximately homogenous laser beam emerges centrally, is known from German Patent No. 44 24 729 C1.
A disadvantage of all the resonators described above is that the course of the beam in the resonator volume depends very heavily on the precise adjustment of all components which enclose the resonator volume. Even in the event that only one single mirror requires adjustment, any angular deviation--no matter how slight would result in a clearly out-of-center beam path and, therefore, inferior beam quality. The above adjustment problems, as well as the use of additional folding mirrors, frequently make it more difficult if not impossible to ensure adequate beam quality.